Such a steering is known from, for example, DE 10 2004 021 531 A1.
Such a hydraulic steering is preferably used in tractors or other self-propelled working machines, which are driven in different environments. For example, a tractor must be able to drive on a public road to and from a field. Its real work is then performed, when it is driving in the field. When driving in the street a steering behaviour is desired that corresponds to that of a normal vehicle. This means that the driver must be able to feel a feedback of the steered wheels on the steering handwheel. For this purpose, it is necessary that the steering unit has feedback behaviour. Such a steering unit then also has the advantage that a “self alignment” of the vehicle can take place, that is, the steered wheels can automatically move to the straight forward position, which the driver learns by means of the turning of the steering handwheel. In many cases, such feedback behaviour is not desired when driving in the field. Otherwise, the driver would have to constantly act upon the steering handwheel or another steering member with a certain force.
In the steering shown in DE 10 2004 021 531 A1, the feedback suppression device has a valve that is located in a working pipe between the steering unit and the steering motor. This valve is electrically activated and opens, when the steering handwheel is activated. Therefore, a certain effort is required to activate this valve.